This invention relates to a suction duct which is associated with a bale opener and through which fiber tufts detached by the bale opener from fiber bales containing cotton, chemical fibers or the like are removed by a suction air stream. The bale opener is of the type which has at least one opening roller mounted in a housing and the detached fiber tufts are entrained by the suction air stream and guided in the suction duct which includes two upwardly extending oblique wall faces (air guiding faces) spaced from one another parallel to the axis of the opening roller.
In a known apparatus, inside the housing two opening rollers and a suction duct are mounted. At the air intake side of the suction duct, in the edge zone above the opening rollers and underneath the suction nipple there is provided a short oblique surface which projects to such an extent into the suction duct as permitted by the maximum deviation of a recessed fiber bale from the line of guidance. As a result, the tuft-laden air stream is admitted through a short path into the suction nipple from the edge zone. Further, a long oblique surface is provided which extends over the length of the opening rollers and begins on one side at a distance above the opening rollers and terminates on the other side at the upper edge of the suction nipple. The tuft-laden air stream flowing from the other edge zone is thus admitted through a longer path into the suction nipple. By virtue of the fact that the long oblique surface starts at a significant distance above the opening rollers, in the edge zone of the suction duct, on the side which is oriented away from the travelling tower of the bale opener, a dead space is present in which undesired eddy currents (turbulences) are generated.